To speed up bulk loading of data, InnoDB implements an insert buffer, a special index in the InnoDB system tablespace that buffers modifications to secondary indexes when the leaf pages are not in the buffer pool. Batched merges from the insert buffer to the index pages result in less random access patterns than when updating the pages directly. This speeds up the operation on hard disks.
In MySQL 5.5, the insert buffer has been extended to a change buffer, which covers all modifications of secondary index leaf pages. This will improve the performance of bulk deletes and updates, transaction rollback and the purging of deleted records (reducing the “purge lag”).
To assess the benefits of the extended buffering, you may want to run benchmarks with the settings innodb_change_buffering=all, innodb_change_buffering=inserts, and innodb_change_buffering=none. Users of solid-state storage, where random reads are …
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